Displaced Christians who fled the violence in Mosul, pray at Mar Aframa church in the town of Qaraqoush on the outskirts of Mosul. Iraq was home to an estimated 1 million Christians before the 2003 U.S.-led invasion that ousted Saddam Hussein. Since then, militants have frequently targeted Christians across the country, bombing their churches and killing clergymen. Under such pressures, many Christians have left the country. Church officials now put the community at around 450,000.

The comments from Nouri al-Maliki come a day after the expiration of a deadline imposed by the Islamic State group calling on Christians in the militant-held city of Mosul to convert to Islam, pay a tax or face death. Most Christians opted to flee to the nearby self-rule Kurdish region or other areas protected by Kurdish security forces.

“What is being done by the Daesh terrorist gang against our Christian citizens in Ninevah province, and their aggression against the churches and houses of worship in the areas under their control reveals beyond any doubt the extremist criminal and terrorist nature of this group,” al-Maliki said in a statement released by his office, using the Arabic acronym for the Islamic State group.

“Those people, through their crimes, are revealing their true identity and the false allegations made here and there about the existence of revolutionaries among their ranks.”

At the Vatican, Pope Francis expressed his concern Sunday for Mosul’s Christians, offering prayers for Iraqi Christians who “are persecuted, chased away, forced to leave their houses without out the possibility of taking anything” with them.

Residents in Mosul also say the Islamic State group’s fighters recently have begun to occupy churches and seize the homes of Christians who have fled the city.

These actions stem from the harsh interpretation of Islamic law the group seeks to impose on the territory it controls in Iraq and neighboring Syria. Already in Mosul, the extremist group has banned alcohol and water pipes, and painted over street advertisements showing women’s faces. It has, however, held off on stricter punishments so far.

Iraq’s Christian communities date back to the first centuries of the religion. Before the 2003 U.S-led invasion, around 1 million Christians called Iraq home. But since then, the community has been a frequent target for militants, and attacks prompted many Christians to leave the country. Church officials now estimate the community at around 450,000.

U.N. Secretary-General Ban Ki-moon strongly condemned “the systematic persecution of minority populations in Iraq by Islamic State and associated armed groups,” in particular the recent threats against Christians in Mosul, according to a statement released Sunday.

Ban also expressed concern about abductions and killings of minority Yazidis, Turkmens and Shabaks, and reiterated that targeting a population because of its ethnic background or faith could constitute a crime against humanity. He also said the U.N. would intensify its efforts to address the urgent humanitarian needs of the displaced.

Prime Minister Al-Maliki, who has ruled the country since 2006, is under pressure to step aside and not seek a third consecutive term. Many in Iraq accuse al-Maliki’s Shiite-led government of helping fuel the crisis by failing to promote reconciliation with the Sunni Muslim minority, and say he has become too polarizing a figure to unite the country and face down the militant threat.

Iraq’s new parliament elected a new speaker last week — the first step toward forming a new government. Lawmakers are expected to meet Wednesday to possibly vote on a new president. By custom, the largely ceremonial post goes to a member of the Kurdish minority.

Ala Talabani, a lawmaker from the Patriotic Union of Kurdistan, said the party had narrowed its choices of presidential candidates down to two names: former deputy prime minister Barham Saleh, and former parliament speaker Fouad Massoum. Talabani, who took part in the discussions Sunday, said the Kurds would decide on one name by Wednesday.

If parliament were to elect a new president this week, that would start the clock on the selection of a new prime minister, increasing the pressure on al-Maliki to bow out.

So far, Iraq’s security forces have struggled to claw back any of the ground they have surrendered to the militants over the past five weeks. The only major counteroffensive has failed to make major headway in retaking the northern city of Tikrit.

The insurgents, meanwhile, have not made any further major gains since overrunning the majority of Iraq’s predominantly Sunni areas. But they continue to attack government forces across several fronts, while also carrying out smaller scale attacks in Baghdad.

The Islamic State group claimed responsibility late Saturday for four bombings in Baghdad which were among a string of attacks that killed at least 27 people earlier in the day. It said two of the attacks were carried out by suicide bombers — Abu al-Qaaqaa al-Almani and Abu Abdul-Rahman al-Shami. The names indicate they were German and Syrian respectively.

The authenticity of the Islamic State group’s statement could not be independently verified, but it was posted on a militant website frequently used by it.